[1] Following graduation, Herrero began to work as the prosecutor of the provincial court in Castellón.
[1] He served in the civil government and the provincial headquarters of the FET in Castellón in 1955 and in Logroño in 1956.
[1] In 1961 he was appointed deputy secretary general of the FET, and on 30 September 1965 he was named the prosecutor of the Supreme Court.
[3] On 5 March 1975 he was appointed secretary general of the movement to the cabinet led by Prime Minister Arias Navarro replacing Utrera Molina in the post.
[4][5] His another son, Luis Herrero, is a journalist and a former Member of the European Parliament for Spain.